Power transmission



Feb, 2, 1943. c. v. LOSEY EI'AL 2,310,100

POWER TRANSMISSION Filed Feb. 12, 1940 LL a FIG. I 36 m FIG. 2

INVENTORS CLIFFORD v. LOSEY &

BY RUDOLF E. EiCH ATTORNEY Patented Feb. 2, 1943 UNITED STATES PATENT OFFICE WDWER TRANSMSSEGN Clifford V. Losey, Detroit, Mich, and Rudolf E.

Esch, Cleveland, Qhio, designers to Vichcra lincormrated, Detroit, Mich a corporation oi Michigan Application February 12.1%0, Serial No. 333.5%

s claims. (or. 121-38) relatively light spring for biasing the valve.

Valves of this character have gone into extensive use and have been found admirablysuitable for their intended purpose in -a great many installations. It has been found, however, that in certain installations, where the fluid motor or other load device which is connected to the outlet port of the valve is of such character that it, in itself, maintains a back pressure in the valve outlet chamber, some dimculty is occasionally experienced. This difiiculty consists in a delayed opening of the reducing valve when flow therethrough is reversed by connecting the normal inlet chamber of the valve to exhaust.

It is an object of the present invention to provide an improved valve of the character described together with an improved control circuit therefor which will insure that the valve will open wide immediately upon the inlet chamber being connected to exhaust.

It is also an object to provide an improved valve of the character described which avoids certain chattering diificulties occasionally exas an electric motor 92, and having a suction conduit id for withdrawing oil from a tank It. A delivery conduit it extends through a relief valve 26 of conventional construction for bypassing the pump delivery to tank through a conduit 22 whenever a predetermined pressure is ex- I ceeded in the delivery conduit it.

The conduit it extends to the pressure port as of a conventional four-way directional control valve 26. The latter has tank ports 28 and 38 which are connected by a return line 32 to the I tank 83. The delivery conduit 18 and the return conduit 32 may have branches 3% and 38 extending to other control valves for directing the pump delivery at times to other fluid consuming devices which normally impose a high pressure on the delivery conduit It.

The. valve 25 has cylinder ports 38 and 50. A conduit 12 extends from the port 38 to the inlet port i i of a pressure-reducing valve 58. The outlet port 18 thereof extends by a conduit 58 to one end of a cylinder 52 having a piston 54 slidable therein. The rod 58 of the piston may be connected to any suitable device, such as a machine tool slide, which it is desired to actuate hydraulically in a reciprocating movement. A conduit 58 extends from the cylinder port at to I the opposite end of cylinder 52 and has a branch to extending to the drain port 62 of the valve 56. Referring now to Figure 2, the valve til is there shown in cross section and may be similar to the valve disclosed in the Harrington patent perienced in certain unusual installations where the resonant characteristics of the circuit are apparently such as to cause occasional chattering with a. valve of the type disclosed in the aforesaid Harrington patent.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred form of the present invention is clearly shown.

In the drawing:

Figure 1 is a diagrammatic view of a hydraulic circuit incorporating a preferred form of the present invention.

' Figure 2 is a longitudinal sectional View of the improved reducing valve incorporated in the circuit of Figure 1.

Referring now to Figural, there is shown a pump ill driven by a suitable prime mover, such with the additional provision of chatter-preventing means iater to be described. Briefly, the valve comprises an inlet chamber 54 which communicates with the port at and an outlet chamber 65 which communicates with the port 58. A valve seat $8 forms a passage between the two chambers and is controlled by a poppet valve is having a. piston 12 of the same diameter as B8 to the control chamber IS and has a pin 82 therein of slightly less diameter than the passage side of the valve 99 connects with the drain port 82. A passage 89 connects between passage 88 and the drain port 82 and has a. check valve 9| therein which opens freely to flow from port 62 to passage 88.

The lower end cap 98 has formed therein a cylindrical bore 98 in which a. piston I is slidablv mounted. The piston is adapted to abut the lower end of valve and for this purpose is biased upwardly by a spring I02 exerting a lighter force than that of spring 18. A restricted passage I04 extends through the piston I00 to communicate between the cylinder 88 and the outlet chamber 66. The bore I00 is of such resistance that oil can flow into or out of the cylinder 98 only at a reduced rate thus restricting the speed of movement of piston I00 equally in both directions.

In operation, with the motor l2 working and driving the pump I0, oil is withdrawn from the tank 18 through suction conduit It and delivered through delivery conduit l8 and branch 30 to the work circuit which is connected thereto causing a pressure to be built up therein.

When it is desired to operate the piston 50 at a lower pressure than that maintained in conduit I8, the spool of valve'26 may be shifted to the left connecting port 20 to port 38 and port 00 to port 30. Pressure fluid is. therefore, permitted to flow through conduit 42, valve 46 and 'conduit 50 to the righthand end of cylinder 52 projecting the piston 50 to the left. The oil discharged from the lefthand end of cylinder 52 returns to tank through conduit 58, valve 26 and conduit 32. During this flow the reducing valve G8 operates to prevent pressure in conduit 50 from building up beyond the value determined by the setting of spring 92, its action in this respect being identical to that described in the Harrington patent. v

It will be noted that the port 82 is, under these conditions, connected to tank by the action of the four-way valve 28. Thus the small leak-oil flow which takes place from outlet chamber Eli through passage 80, chamber i8, passage 88, valve 90, and port 62 maintains a balanced load on the upper end of piston I0 which load automatically varies to adjust the valve ill to whatever position may be necessary to maintain in chamber 66 a predetermined pressure. During this action the piston I00 acts to restrict the speed of movement of valve 10 only in the downward direction since the valve I0 cannot move downwardly without also moving the piston H00 downwardly, and its speed is dependent upon the rate at which oil can discharge from cylinder 98 through passage I00. During upward movement of the valve I0 the piston I00 imposes no restriction to its speed since the valve I0 is free to lift away from the piston I00 whenever pressure conditions in chambers 88 and I6 cause such upward movement. Thus any tendency to chatter which may arise from the resonant characteristics of the circuit is eflfectively damped out by retarding movement of the piston I2 in one direction.

When it is desired to return the piston 54 toward the right, the spool of valve 28 may be shifted to the right thus connecting port 24 to port 40 and port 38 to port 28. Under these conditions it will be noted that pressure oil directed through conduit 58 to the leithand end of cylinder 52 is also directed through the branch conduit 80 to the drain port 62 thus building up pressure behind. the valve 90 causing the latter to close in the same manner as a check valve. Check valve 9I'permits the pressure fluid to flow ireely through passages 88 and 88 to the chamber I8 thus positively pushing the piston I2 downwardly to open valve 10 immediately. Accordingly. return flow lrom the righthand end of cylinder 62 is permitted to flowi'reely through conduit 50, valve 48 and conduits 42 and 32 back to the tank.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope oi the claims which iollow.

What is claimed is as follows:

1. A hydraulic power transmission system comprising in combination with a fluid motor and a source of pressure fluid, two conduits leading to opposite sides of the motor, directional control means for selectively directing pressure fluid to either conduit selectively while exhausting the other conduit, a pressure reducing valve in series in a first one of the conduits, said valve having an operating chamber for controlling the opening and closing of the valve, and means including a branch conduit connecting between the operating chamber and the second one of the conduits for fully opening the reducing valve while the second conduit is under pressure.

2. A hydraulic power transmission system comprising in combination with a fluid motor and a source of pressure fluid, two conduits leading to opposite sides of the motor, directional control means for selectively directing pressure fluidto either conduit selectively while exhausting the other conduit, a pressure reducing valve in series in a first one of the conduits, said valve having an operating chamber for controlling the opening and closing of the valve, means forming a path for a relatively small fluid flow from the outlet of the reducing valve through the operatingchamber to a point outside the valve, and means for selectively conducting such flow to exhaust or inhibiting such flow.

3. A hydraulic power transmission system comprising in combination with a fluid motor and a source of pressure fluid, two conduits leading to opposite sides of the motor, directional control means for selectively directing pressure fluid to either conduit selectively while exhausting the other conduit, a pressure reducing valve in series in a first one of the conduits, said valve having an operating chamber for controlling the opening and closing of the valve, and means under the control of the directional control means for selectively connecting the operating chamber either with pressure fluid or exhaust.

4. A hydraulic power transmission system comprising in combinationwith a fluid motor and a source of pressure fluid, two conduits leading to opposite sides of the motor, directional control means for selectively directing pressure fluid to either conduit selectively while exhausting the other conduit, a pressure, reducing valve. in series in a first one of the conduits, said valve normally acting to prevent reverse flow therethrough, and pilot control means for selectively opening the valve to reverse flow.

5. A hydraulic power transmission system comprising in combination with a. fluid motor and a source of pressure fluid, two conduits leading to opposite sides of the motor, directional control means for selectively directing pressure fluid to either conduit selectively while exhausting the other conduit, a pressure reducing valve in series in a first one of the conduits, pressure responsive pilot means for regulating the opening of the valve to maintain a predetermined pressure at the outlet thereof, and fluid pressure means for selectively disabling said pilot means.

6. A hydraulic power transmission system comprising in combination with a fluid motor and a source of pressure fluid, two conduits leading to opposite sides of the motor, directional control means for selectively directing'pressure fluid to either conduit selectively while exhausting the 

